Current Events Discussion

[Harbles]

Oh well yes I guess now that they are taking science they may want to hold some info close.
That is a new development though.

This still works! http://cmsdoc.cern.ch/events/snapshotA1.png
I hope

[Xymox]

hehehee... Yes things from the log would require a password...

[Kasuha]

These long physics runs are sure great achievement but they're starting to be boring. I hope they'll start doing some interesting stuff like injecting more bunches or even bunch trains soon...

[Harbles]

Seems to work again this morning, It's from CMSTV http://cmsdoc.cern.ch/cmscc/cmstv/cmstv ... frames=yes which i don't think is behind a pw, but mine might auto load from the 2 computers I watch on (home & work). Like I said it wasn't working last night and now it does again so I'm happy

[LarryS]

Beam was lost due to an Undulator Trip from the QPS (Quench Protection System)

Does anyone know what an "Undulator" is ? ...

[Kasuha]

Does anyone know what an "Undulator" is ? ...

Wikipedia does
Some undulators are mentioned in this chapter of design report, looks like in some place they bend the beam to one side and back to generate synchrotron light then used to monitor beam position.

[LarryS]

Thanks ... that makes sense

[morgad]

These long physics runs are sure great achievement but they're starting to be boring. I hope they'll start doing some interesting stuff like injecting more bunches or even bunch trains soon...

to quote from the last page of this mornings meeting (on the 'progress page')and add some highlighting

Incoming
Stable beams
18 hours machine stop – Thursday 06:00
b3 - at injection
Track Q’(t) (and Q(t)), unload lattice sextupoles from b3 error
Ramp
B3/Q’ – snapback - track Q’ in first part of ramp
Orbit feedback
Collimators
Squeeze
Revisit mechanics & iterate
Collimation and stable beams
Injection
Higher intensities

could be en interesting weekend coming up :-)

Dave

[jmayes]

Seems to work again this morning, It's from CMSTV http://cmsdoc.cern.ch/cmscc/cmstv/cmstv ... frames=yes which i don't think is behind a pw, but mine might auto load from the 2 computers I watch on (home & work). Like I said it wasn't working last night and now it does again so I'm happy

Working for me too now, I was getting a server load error so might have been too many people hitting it. That's not real good, they will lock us out if we overwhelm them.

[ali]

Right now (1800 CH time) it says there was an unprogrammed dump during tune trim. Does this mean the beam was lost while tweaking some of the parameters, hitting the side of the beam tube?

If so does the energy released damage the tube? And if there were higher intensity beams could this ever cause a quench?

Thanks for your time, ali.

[oxodoes]

Yes the beam was lost! But this happens rather often and you will get used to it very soon . Tune refers to the number of transversal oscillations of the beam envelope during one turn in the machine. (The tune is vitaly important for the stability of the beam as there might be resonances.) Dump means that the beam was directed onto a graphite block, for a safe release of the energy, before it got completely out of hand.

Higher intensities have the potentional to seriously damage the machine (including quenches), but collimators are installed around the ring to absorbk particles that are off track before they hit the beam tube.

[pixelmasseuse]

I see the comments now say: Preparing for ramp, then squeeze test.

I saw in one of the LHC docs there was some discussion of squeezing during ramp-up vs. squeezing at full energy, so I am wondering if they will now try squeezing during ramp-up.

[ali]

Yes the beam was lost! But this happens rather often and you will get used to it very soon . Tune refers to the number of transversal oscillations of the beam envelope during one turn in the machine. (The tune is vitaly important for the stability of the beam as there might be resonances.) Dump means that the beam was directed onto a graphite block, for a safe release of the energy, before it got completely out of hand.

Higher intensities have the potentional to seriously damage the machine (including quenches), but collimators are installed around the ring to absorbk particles that are off track before they hit the beam tube.

Hi Oxodoes, many thanks for your answer, I don't quite understand the tune and resonances though - do you use tuning to stabilise the beam by removing the resonances?

Cheers, ali.

[oxodoes]

see here: http://lhcportal.com/Forum/viewtopic.php?f=4&t=219

[ali]

see here: http://lhcportal.com/Forum/viewtopic.php?f=4&t=219

thanks again. I began to read this a while ago but didn't make it to the end, that clears things up this time round though.